280 FRANZ SCHRADER 
cell division and other abnormalities are not uncommon in such 
structures. 
A very striking feature observed at certain stages is the pres- 
ence of very definite tubules interspersed through the cytoplasm. 
These may stand in some relation to the symbionts described by 
Buchner, although the latter apparently did not see them in the 
European species he examined. ‘They are in some respects very 
similar to Holmgren’s canals, but, unlike the latter never extend 
to the periphery of the cell. In division they are placed immedi- 
ately around the spindle. Their distribution seems haphazard 
at this stage. After division they appear to break up into gran- 
ules, only to be reformed immediately afterward, but I am not 
prepared to maintain that this phenomenon may not be due to 
fixation. 
I made some attempts to determine the nature of these struc- 
tures—whether mitochondrial or otherwise. The poor preserva- 
tive action of osmic mixtures when used in connection with these 
cells eliminated the Benda stain at the outset. The mixture of 
formalin and potassium bichromate employed by Kopsch gave 
very good fixation at times, and, when used in conjunction with 
- Kull’s modification of the Altmann stain, gave some excellent 
preparations. Here, as in certain gland cells of Myxine, recently 
studied by Schreiner (’16), the nucleolus and the thread-like in- 
clusions stain red, while the chromatic material is a faint green. 
Such a stain is not very specific, however, for, as Professor Wilson 
pointed out to me, the acid fuchsin is apt to stain any cytoplasmic 
inclusion, regardless of its nature. Janus green used on fresh 
material did not stain the structures in question, but such nega- 
tive evidence does not carry much weight. The tubules stained 
a deep black with haematoxylin. When fixed with the Gilson- 
Carnoy fluid, part of the tubule or what may be called the matrix 
disappeared, leaving a spiral skeleton or framework which re- 
tained the haematoxylin stain and still showed the tubular 
structure. Such pictures give the impression that they are com- 
posed of two different substances, only one of which is dissolved 
by the action of the strong fixing agent. 
